阳泉市区夏季挥发性有机物污染特征、来源解析及其环境影响

Characteristics,Source Apportionment,and Environmental Impact of Volatile Organic Compounds in Summer in Yangquan

采集阳泉市区夏季3个监测点的环境空气样品,利用气相色谱-质谱/氢火焰离子化检测器(GC-MSD/FID)测定了挥发性有机物(VOCs)的组成,研究了其浓度特征,运用特征比值法和正定矩阵因子分析模型(PMF)解析了VOCs来源,评估了VOCs对O3和二次有机气溶胶(SOA)生成的影响.结果表明,阳泉市区VOCs平均总浓度为(82.1±22.7)μg·m-3,其中烷烃浓度占比最大(51.8%),其次是芳香烃(17.8%)和烯烃(8.0%),炔烃浓度占比最小(3.8%). VOCs呈现双峰的变化特征,分别于08:00~10:00和18:00~20:00出现峰值,在12:00~14:00出现谷值.苯/甲苯和异戊烷/正戊烷的均值分别为2.1±1.3和1.7±0.6,表明环境空气VOCs可能受燃煤排放和机动车排放的双重影响. PMF解析出VOCs来源分别为燃煤源(34.9%)、机动车排放源(18.2%)、汽油挥发源(15.2%)、工业排放源(13.6%)、植物排放源(9.2%)和溶剂使用源(9.0%). VOCs臭氧生成潜势(OFP)均值为156.6μg·m-3,烯烃贡献最大,二次有机气溶胶生成潜势(SOAp)均值为68.7μg·m-3,芳香烃的贡献达到93.4%.总之,燃煤排放对VOCs的贡献较高,因此,控制燃煤源排放是阳泉市区VOCs管控重点,需加快矸石山治理和能源结构调整,同时机动车排放源、汽油挥发源和工业排放源的管控也不容忽视.

Volatile organic compounds(VOCs)were collected at three environmental sampling sites in Yangquan and quantified by gas chromatography-mass selective detector/flame ionization detector(GC-MSD/FID).The VOC sources were identified by diagnostic ratios and positive matrix factorization(PMF),and environmental impact of VOCs on O3 and secondary organic aerosol(SOA)were evaluated.The results showed that the average VOC concentration was(82.1±22.7)μg·m-3,with alkanes being the most abundant group(51.8%),followed by aromatics(17.8%),alkenes(8.0%),and alkynes(3.8%).The diurnal variation of VOCs exhibited a bimodal trend,with twin peaks appearing at 08:00-10:00 and 18:00-20:00,falling to a valley at 12:00-14:00.The results for benzene/toluene(2.1±1.3)and isopentane/n-pentane(1.7±0.6)showed that the ambient VOCs may be influenced by coal combustion and vehicular emissions.Six sources were extracted by PMF:coal combustion(34.9%),vehicle emissions(18.2%),gasoline evaporation(15.2%),industrial emissions(13.6%),biogenic emissions(9.2%),and solvent usage(9.0%).The average concentration of ozone formation potential(OFP)was 156.6μg·m-3,with the highest contribution from alkenes,while the average concentration of secondary organic aerosol formation potential(SOAp)was 68.7μg·m-3,mainly from aromatics(93.4%).In summary,coal combustion was the most abundant source of VOCs,and accelerating the management of coal gangue and energy structure readjustment are the key points to address.Meanwhile,restricting the VOCs from vehicle emissions,gasoline evaporation,and industrial emissions is also required.